The Registration.aspx.cs file is setting the link (in code-behind). Here is the line:
EventExportLink.NavigateUrl = string.Format("/Event.axd?type=registration&id={0}", Campaign.Id);
Then in your web.config, there is an http handler that is registered for Event.axd.
If you are seeing it working in dev but not on prod, I would suspect that this is an issue of developing on a different version of IIS than your production, and possibly a difference in the application pool mode, or of running the portal in Cassini in development.
Long story short, we tried to get all of the permutations of IIS settings (from IIS 6, 7, and now 7.5) to be compatible in the published web.config file. There are two different sections in the web.config file that this event handler is wired up in.
I would recommend reviewing the web.config file that you deployed to production to ensure that the handler is still there. And in case you are wondering, the best configuration is on IIS 7 (Windows 2008, 2008 R2, Windows 7) and using an integrated pipeline
(not classic).
Shan McArthur www.shanmcarthur.net Check out the commercial edition of xRM portals @ www.adxstudio.com